1. Field of the Invention
The present invention pertains to a rolling mill that includes a roller assembly through which a heated piece of metal is passed in order to produce a progressively thinned and elongated metal sheet which is then cooled and, more particularly, to a nozzle arrangement for use in directing a flow of cooling fluid upon a heated sheet of metal in a rolling mill.
2. Discussion of the Prior Art
Rolling mills are commonly used for producing elongated metal sheets for various applications. In general, such rolling mills receive a slab of metal which is heated and is caused to pass between at least one pair of rollers of a roller assembly in order to thin and lengthen the metal slab. In certain known types of rolling mills, the slab is serially passed through various roller assemblies in a heated state. Each of these roller assemblies have associated spacings through which the metal slab passes which are progressively made smaller such that the slab is continually thinned as it passes through the rolling mill until an elongated metal sheet is produced. The elongated metal sheet can then be wrapped by means of a coiler for various uses:
Due to the number of and required spacing between the various roller assemblies in such a rolling mill, it has also been heretobefore proposed to produce an elongated metal sheet from a metal slab by utilizing a reverse rolling or steckel mill. FIG. 1 schematically illustrates a typical milling operation incorporating a steckel mill. This milling system, generally indicated at 1, receives a supply of metal from a continuous casting machine 5. Instead of continuous casting machine 5, a slab of metal can also be introduced into the milling system 2 upon a conveyor indicated at 7. Conveyer 7 delivers the metal through a heating furnace 9 and, if necessary, through a roughing roller-type mill unit 11. In some applications, roughing roller-type mill 11 is made reversible such that the slab or metal can be passed therethrough various times in order to obtain a slab having a certain thickness which is then passed to the steckel mill generally indicated at 15. Once the metal is elongated into a sheet in steckel mill 15, it proceeds to a cooling zone 18 and then is delivered over a guide roller 21 to a coiling device 24.
Steckel mill 15 typically includes first and second coil furnaces located within housings 28 and 29. Housings 28 and 29 each rotatably house a drum 32, 33 which are adapted to alternatively coil and uncoil a strip of metal indicated at 38. Metal strip 38, for instance, extends through an opening 40 in first housing 28, between rollers of a guide unit 42, between the rollers of a rolling mill assembly generally indicated at 46, through a second guide roller unit 48 and into second housing 29 through an opening 50. As is known in the aft, the area through which strip 38 must pass within rolling mill assembly 46 is adjustable such that, as strip 38 is repeatedly passed through milling roller assembly 46 and alternatively coiled within housings 28 and 29, the thickness of strip 38 is systematically reduced commensurate with the elongation of strip 38. In order to maintain strip 38 in a flexible state for coiling and to enable strip 38 to be thinned out as it is passed through milling roller assembly 46, each housing 28 and 29 includes a coil furnace as discussed above to heat strip 38.
For this purpose, known steckel mills generally incorporate a plurality of burners which operate at a temperature in the order to 2000.degree.-3000.degree. F. Therefore, the temperature of the sheet that passes from steckel mill 15 to cooling zone 18 is extremely hot and must be sufficiently cooled down prior to delivery to coiling device 24. Sheets of metal produced in other types of rolling mills are similarly heated, although perhaps to a lower extent, and subsequently cooled as well.
It is known in the milling art to deliver the hot sheet of metal between upper and lower banks of nozzles through which cooling fluid is sprayed unto the upper and lower surfaces of the metal sheet within cooling zone 18. As illustrated in FIGS. 2a-2c, such known nozzles are generally formed from various components. More specifically, each nozzle 50 includes a head portion 53, a substantially cylindrical body portion 57 and a plurality of baffle or diffuser members 60, 61. The head portion 53 includes a terminal end 65 that is formed with a plurality of flats 68 for receiving a tool for securing nozzle 50 to a header (not shown). For this purpose, head portion 53 is also formed with a threaded portion 70, adjacent terminal end 65, which is adapted to be threadably secured to a respective header.
The cylindrical body portion 57 is crimped to head portion 53 at 74 when an annular rim 76 of cylindrical body portion 57 is seated against a plateau 78 formed in head portion 53. Baffle member 60 is positioned within cylindrical body portion 57 and abuts annular edge 80 of head portion 53 and baffle member 61 is located adjacent a flared end 83 of cylindrical body portion 57 as best shown in FIG. 2b.
This known nozzle construction suffers from various drawbacks. First, head portion 53 is currently made of brass and cylindrical body portion 57 of copper. Therefore, these components need to be assembled and, due to the extreme temperatures and corrosive environment to which nozzles 50 are subjected in the rolling mill, nozzles 50 need to be replaced on a regular basis. Due to the construction and materials from which the known nozzles are made, replacement is extremely expensive. In fact, a typical mill generally utilizes in the order of 1500-2000 such nozzles within cooling zone 18, and with this known construction, replacement of each nozzle generally runs in the order of several hundred dollars if purchased individually. Of course, the cost can be substantially reduced if the nozzles are purchased in large quantities. A typical rolling mill constructed in the manner set forth above and utilizing the known nozzles consumes approximately 1500 nozzles a year. Therefore, periodic replacement of the nozzles represents a substantial financial expenditure.
Second, it is extremely desirable to maintain a laminar flow through each nozzle 50 such that the spacing between adjacent nozzles can be accurately determined in order that the sheet metal can be evenly cooled. This does not occur with the known nozzle construction of FIGS. 2a-2c. Instead, turbulences are created due to the presence of annular edge 80, which represents an abrupt diameter change between the flow of cooling fluid from within cylindrical body portion 57 to head portion 53, and the spacing of baffle members 60, 61 which often leads to non-laminar flow changes therebetween.
Based on the above, there exists in the art of rolling mills, and particularly in a cooling zone thereof, a need for a nozzle arrangement which is constructed in a manner which will enable a laminar flow of cooling fluid therethrough to be maintained and which represents a relatively inexpensive alternative to known nozzle arrangements in this field.